Independent experts have pinpointed what they believe to be the Euphrates River site in Syria that was bombed by Israel last month, and satellite imagery of the area shows buildings under construction roughly similar in design to a North Korean reactor capable of producing nuclear material for one bomb a year, the experts say.

Photographs of the site taken before the secret Sept. 6 airstrike depict an isolated compound that includes a tall, boxy structure similar to the type of building used to house a gas-graphite reactor. They also show what could have been a pumping station used to supply cooling water for a reactor, say experts David Albright and Paul Brannan of the Institute for Science and International Security (ISIS).

U.S. and international experts and officials familiar with the site, who were shown the photographs yesterday, said there was a strong and credible possibility that they depict the remote compound that was attacked. Israeli officials and the White House declined to comment.

If the facility is confirmed as the site of the attack, the photos provide a potential explanation for Israel's middle-of-the-night bombing raid.

The facility is located seven miles north of the desert village of At Tibnah, in the Dayr az Zawr region, and about 90 miles from the Iraqi border, according to the ISIS report to be released today. Albright, a former U.N. weapons inspector, said the size of the structures suggested that Syria might have been building a gas-graphite reactor of about 20 to 25 megawatts of heat, similar to the reactor North Korea built at Yongbyon.

"I'm pretty convinced that Syria was trying to build a nuclear reactor," Albright said in an interview. He said the project would represent a significant departure from past policies. ISIS, a nonprofit research group, tracks nuclear weapons and stockpiles around the world.

Israel, which has nuclear weapons of its own, has not said publicly what its warplanes hit or provided justification for the raid. Syria has denied having a nuclear program. But beginning construction of a nuclear reactor in secret would violate Syria's obligations under the Non-Proliferation Treaty, which requires all signatories to declare their intent when such a decision is made, according to sources at the International Atomic Energy Agency, the U.N. nuclear watchdog.

The new report leaves many questions unanswered, such as what Syria intended to use the unfinished structures for and the exact role, if any, of North Korea in their construction. Also unclear is why Israel chose to use military force rather than diplomatic pressure against a facility that could not have produced significant nuclear material for years. The new details could fuel debate over whether Israel's attack was warranted.

Albright acknowledged the difficulties of proving what the site is, in part because the roof was put on at an early stage, blocking views of the foundation and obscuring any potential reactor components. In construction of other types of nuclear reactors, the roof is left off until the end so cranes can move heavy equipment inside.

Some nuclear experts urged caution in interpreting the photos, noting that the type of reactor favored by North Korea has few distinguishing characteristics visible from the air. Unlike commercial nuclear power reactors, for example, a North Korea-style reactor lacks the distinctive, dome-shaped containment vessel that prevents the release of radiation in the event of a nuclear accident.

"You can look at North Korea's [reactor] buildings, and they look like nothing," said John E. Pike, a nuclear expert and director of GlobalSecurity.org. "They're just metal-skinned industrial buildings." The proximity of the building to a water source also is not significant by itself, Pike said.

But Brannan, of ISIS, combed through a huge amount of satellite imagery to find a site along the Euphrates that matches a reactor's specifications as well as descriptions of the attack site. The compound's distance from populated areas was a key detail, since reactors are usually isolated from major urban populations.

The site is also close to an irrigated area, which would explain statements by some officials privy to details of the attack that the facility was located near orchards. A small airstrip about two miles away could have been used to transport personnel to the site.

U.S. and foreign officials tracking the incident said that Syria is presently trying to remove remaining structures at the site.

The International Atomic Energy Agency has acquired its own aerial photographs but has not finished analyzing them, according to an IAEA source.

In an interview published yesterday, IAEA director and Nobel Peace laureate Mohamed ElBaradei expressed anger at the Syrians, Israelis and foreign intelligence agencies for not providing information about a suspected nuclear program.

"We have said, 'If any of you has the slightest information showing that there was anything linked to nuclear, we would of course be happy to investigate it,' " he told the French newspaper Le Monde. "Frankly, I venture to hope that before people decide to bombard and use force, they will come and see us to convey their concerns."

ElBaradei also said an airstrike could endanger efforts to contain nuclear proliferation.

"When the Israelis destroyed Saddam Hussein's research nuclear reactor in 1981, the consequence was that Saddam Hussein pursued his program secretly. He began to establish a huge military nuclear program underground," he said. "The use of force can set things back, but it does not deal with the roots of the problem."